[JVM] Restore old implementation of 'lazy gather'
[JVM] Restore old implementation of 'lazy gather'

The performance optimization of 971174f4d8 broke things on the JVM
backend. This is a known problem with nqp::null getting HLLized
showing up again -- cmp. https://github.com/rakudo/rakudo/issues/1613

nbrown/rakudo,rakudo/rakudo,softmoth/rakudo,softmoth/rakudo,tony-o/rakudo,labster/rakudo,rakudo/rakudo,salortiz/rakudo,rakudo/rakudo,labster/rakudo,MasterDuke17/rakudo,nbrown/rakudo,MasterDuke17/rakudo,nbrown/rakudo,salortiz/rakudo,nbrown/rakudo,salortiz/rakudo,labster/rakudo,tony-o/rakudo,softmoth/rakudo,rakudo/rakudo,tbrowder/rakudo,tbrowder/rakudo,MasterDuke17/rakudo,tony-o/rakudo,salortiz/rakudo,labster/rakudo,rakudo/rakudo,salortiz/rakudo,rakudo/rakudo,MasterDuke17/rakudo,salortiz/rakudo,tbrowder/rakudo,nbrown/rakudo,tony-o/rakudo,labster/rakudo,tony-o/rakudo,tony-o/rakudo,softmoth/rakudo,tbrowder/rakudo,softmoth/rakudo,tbrowder/rakudo,labster/rakudo,nbrown/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,MasterDuke17/rakudo